package edu.uci.ics.hivesterix.optimizer.rules;

import org.apache.commons.lang3.mutable.Mutable;

import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.IOptimizationContext;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalOperatorTag;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.SelectOperator;
import edu.uci.ics.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;

public class RemoveRedundantSelectRule implements IAlgebraicRewriteRule {

	@Override
	public boolean rewritePre(Mutable<ILogicalOperator> opRef,
			IOptimizationContext context) throws AlgebricksException {
		return false;
	}

	@Override
	public boolean rewritePost(Mutable<ILogicalOperator> opRef,
			IOptimizationContext context) throws AlgebricksException {
		AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
		if (op.getOperatorTag() != LogicalOperatorTag.SELECT) {
			return false;
		}
		AbstractLogicalOperator inputOp = (AbstractLogicalOperator) op
				.getInputs().get(0).getValue();
		if (inputOp.getOperatorTag() != LogicalOperatorTag.SELECT) {
			return false;
		}
		SelectOperator selectOp = (SelectOperator) op;
		SelectOperator inputSelectOp = (SelectOperator) inputOp;
		ILogicalExpression expr1 = selectOp.getCondition().getValue();
		ILogicalExpression expr2 = inputSelectOp.getCondition().getValue();

		if (expr1.equals(expr2)) {
			selectOp.getInputs().set(0, inputSelectOp.getInputs().get(0));
			return true;
		}
		return false;
	}

}